Why a MERS Vaccine Won't Be Easy

Two years ago, the virus didn't even have a name. A year ago it had infected roughly 50 people, half of whom died. Now, Middle East Respiratory Syndrome has been confirmed in more than 600 people, and killed nearly 30 percent of its victims.

Originating on the Arabian Peninsula, MERS has been carried via travelers to the United States (two reported cases), North Africa, and Malaysia, as well as a handful of European countries.

Adding urgency to the anxiety, the annual pilgrimage to Mecca in early October will draw more than a million people through the city of Jeddah, the outbreak's "ground zero."